This measurement is consistent with 0.22dB loss per metre and 0.25dB for each connector.

(15 x 0.22) + (2 x 0.25) = 3.8dB.Comment on measuring loss in long cables using a VNA.Slow down the sweep time until you get a consistent measurement! I found this out the hard way myself, and, nearly always, whenever customers have challenged the specs on supplied cables it has turned out to be a measurement issue.Peter Martin